High frequency detector



Feb. 23, 1932. E. D, MQA'RTHUR 1,846,888

HIGH FREQUENCY DETECTOR Filed April 19 1929 Inventor'- El mean D.M Arthur,

His Attahn Patented Feb. 23,1932.

"a is i 1,846s8e Ar-ear PMC213- V marina D. -McA-BTHUR, orscnn vncrnnmfivnw yonmnssienon troennnniininnnornro T COMPANY, A conronarron or ran-w :YOBK 1 nrenrnnonnncv m ma I ,7 Application 'filed April 19,

The present invention relates to high frequency detectors of theelectric discharge type, and more particularly to detectors for ultra-high frequencies above the range in which the triode or'three-element electric discharge device is useful, that, is, in the range about 3 meters (lfi'Omegacycles) and below.

A form of highly evacuated electric discharge device having a hot cathode mounted between two anodes in astrong'magnetic field parallel to the axis of the anodes, has been adapted by suitable circuit a and control means in an oscillation generator for the production of undamped and modulated wave signals in the range of frequencies which could not be produced by the ordinary triode in a feedback circuit. A generating circuit and means of this character is shown and described in a copending application of Kinjiro Okabe, Serial No. 285,008, filed June 13, 1928 and assigned to the sameassignee as'the present application. a r

In order to be useful, however, such signals must subsequentlybe detected and received,

and heretofore many attempts have been made to receive signals of such high frequen-l cy, in the range below three meters or above -100'megacycle's for example, without altogether satisfactory results." At such high frequencies or low wavelengths the triode or three-element discharge device cannot be made to. oscillate satisfactorily ina feedback circuit. .Furthermore,the triode isvery unstable at suchhigh frequencies and is difficultto operate.

It is therefore the object of my invention to provide an improved detector for 'undamped and modulated wave signals,and in carrying out my invention 1 have found that a magnetically controlled" electric discharge 7 device of the typeabove mentioned having a split anode maybe used as a heterodyne detector of both types of signals.

My invention will be better understood frontal consideration of the accompanying drawing and the description thereof, and its -scope=will be pointed out in the appended claims, I a v v Inrthe drawmg the figure 1s a wiring ill- 1929. Serial No. 356,535.

agram of tion. l Referring to the drawing, 5 is amagnetically controlled electric discharge device having a split anode, the anodesorsectio'ns of which are indicated at-6' and-7, and together surround a filament or cathode *8 a detector embodying l my in-vensource of energy represented by a-batt'eryIQ,

in circuit with which is connected a var-i able resistor 13 for-controlling-the e xcitati'on 'or strength-of the field whereby the sensitivity of the circuit is controlled as will hereinafter be mentioned. The anodes 6 and'fZ'which may be considered to betwoportions of a split cylinder, are connected with the-"terminals ofan osciillatorycircuit 14 comprising-suitable tuning means such as a fixedinductance'lfi and a variable capacitonlti.

Signals to be received areintrodueedinto the tuned circuit Idfrom any suitable-source and by any suitable means, andiin' th'e present example are introduced into' the-circuit through a coupling coil 17 inductively coupled with the winding or inductance 15. The coupling coilis in turn connected with a suitable collector of radio frequency-energy-represented by'an antenna anid a ground connection 19 T he tuned. r oscillatory circuit'l f' may; be

current center or neutral point indicated in,

the present example at 20-0n -tlie'coil of ,inductance 15. 'lhe neutral point is connected with a lead-21 which returns tothecathode at any suitable pointsuch .asJ-at 22, Inthislead is placed a source ofvoltag'e and energy 23 for exciting the anodes, and an output which at its ends is connected-with a-cathode device24 of any suitable type. In the pres-' ent example this output device is shown as being a transformer, the primary of which provides an audio frequency impedance in the return lead, and the secondary of which is connectedwith asuitable receiving means such as a-pair of telephone receivers 26.

The signal introduced into the tuned circuit 1e from the antenna system is there niade to [beat -with 1 a locally generated oscillation of a definite frequency provided by the electric discharge device, which is determined by the adjustment of variable condenser 16. As a result there flowsin lead 21 between the cathode and the oscillatory circuitan audio frequency component of current which is proportional to the impressed signal. I e e v To make-use of this audio fr uency cure rent a large reactance or impedance is placed in series with this lead, the impedance in the present example being the primary of transformer 24; By a proper design, this impedance may be made to act like afiltcr in that it divides the audio frequency component of the currentfiowing in lead 21 from the radio frequency component. The radio frequency component may be made to flow to the cathode through suitable by-pass'condenser;25.. The audio frequency voltage built .up across impedance 124: is then transferred to an indicating device-which in the present example is a pairof telephone receivers 26 connected with the secondary of transformer 24.

It will be apparent that if the amplification obtained in transformer 24 is insuficient to .produce loudsignals in telephones 25 or other suitable output. device, any suitable additional amplification may be provided by suitable means. 1

I am aware that electric discharge devices of the magnetically controlled type have been used before in high frequency apparatus and that attempts have been made to use them as oscillating detectors, but heretofore they have been subject to the same dimculties as were three-element electric dis- .charge devices or triodes in that the feed back oscillation producing means introduced difliculties in maintaining constant. oscillations at high frequencies or-ultra -high frequencies and the strength of the oscillations was below useful values atsuch'frequencies. Ihavediscovered however, that by'using 'a magnetically controlled electric discharge fdevice'of the type described with the anode 'dlvided into two equal parts, or a split anode.

- I obtain an oscillating detector which does not have high internal capacity as compared to the triode and which will receive undamped wavesignals or modulated wave extremely highfreq'uen'cy signalsyfor example 7 wave lengths below one meter. 7 T The essentials of my-dete'ctor circuit are few and include merely a magnetically controlled split anode electric discharge'olevice,

a tuned oscillatory circuit in connection therewith, the circuit having a tappedneutral point, and an output device providing an impedanceto the modulation or beat frequency si nals, resulting from detection, in the lead from said neutral point. The im-, pedance is usually an audio frequency im -pedance for the audible reception ofthesignals. I

' By-pass condensers and a plurality of choke coils in supply leads as used with ordinary triodes and the like at high frequencies are not required with this split anode circuit for the reasonthatthe, audio frequency or-output circnlt is connected with the mld.

thebare essentials above mentioned and as indicated in the drawing. 'No grid-leak or condenser or bias voltages are required for detector operation with their corresponding lossesand influence upon signals. The circuit is therefore much quieter in operation for the reason that these elements as found in ordinary regenerative receiving circuits" are omitted.

A further advantage of the split anode magnetically controlled electric discharge device as a detector of high frequency signals lies in the fact that there is no regenera tion to control when changing from telegraphic or undamped wave signals to modulated wave'or broadcast signals. The sensitivity may however, be controlled by varying the field'strength of the device between certain limits. These limits lie within a range any value of which would produce cut+oif or stop the current flow were the'anodes connected together for operation as a. single anode.

While it may be used with any'oscillation frequency desired, a detector circuit substantially as shown in the drawing has been found to function with great stability' and to be particularly useful at frequencies at whichthe three electrode tubescannot be made to function. This is in the range of frequencies above 100 megacycles (8 meters). It is 'bedifficulty experienced in obtaining the local oscillations which are necessary forthe freception of continuous wave telegraph signals.

. messes I A split anode magnetically controlled elec-' tric discharge device has been found to operate successfully in producing strong oscillations up to 400 megacycles (0.75 meters). Such oscillations may be broughtup to the order of amperes, it necessary, hence a strong output may be maintained.

-What I claim as new and desire tosecure by Letters Patent of the United States, is,-

1. In combination, a magnetically controlled electric discharge device having a split anode, a tuned oscillatory circuit connected therewith and provided with a center tap, a cathode lead connected to said center tap, and an output device and a'source of divided anode and having a center tap, a lead connecting said center tap and said cathode, a source of energy and an impedance in said cathode lead, and means connected with said impedance for receivingdetected signals.

4. In combination, an electric discharge device having a divided anode, a cathode, means for producing amagnetic field between said cathode and anode, an oscillatory circuit having its terminals connected with said divided anode and having a center tap, a lead connecting said center tap and said cathode, a source of energy and: an inn pedance in said cathode lead, means connect.- ed with said impedance for receiving detected signals, and means for varying. the

strength of the magnetic field between pre-.

determined limits.

5. In combination, an electric discharge device having a divided anode, a cathode, means arranged to produce a magnetic field between said cathode andanode, an oscillatory circuit having its terminals connected with said divided anode and having a center tap, means arranged to apply high frequency signals to said circuit, a lead connecting said center tap and said cathode, a source of energy and an impedance in said cathode lead, means connected with said imedance to receive detected signals, and means arranged to vary the strength of the magnetic field between predetermined limits to 1vary the sensitivity of said circuit to sig na s.

6. A means for detecting undamped and modulated waves of a frequency higher than I '100'megacycles, said means including a mag, netically controlled electric. discharge device having a split anode and a cathode, a tuned oscillatory circuit connected w1thsa1d anode and provided with a neutral point, and

an output device including an impedance con:

nected in circuit with-said neutral point and I the cathode. V i

7. The combination in a carrier wave detector, of anelectron discharge device having a cathode, a pair of anodes arranged adjacent said cathode, means for producing a magnetic field between said anodes, means for impressing a signal modulated carrier wave between said anodes whereby the signals with which said carrier wave is modulated are detected by said discharge device, and means connected to receive the detected signals from said discharge device.

8. The combination in-a carrier wave detector, of an electron discharge device, having a cathode and a plurality of anodes, a circuit connected between said anodes tuned to the frequency of the carrierwave to be detected means for producing a unidirectional magnetic field between said anodesand cathode, means for impressing a received carrier wave upon said tuned circuit, and means connected with said discharge device to re ceive the detected signals.

9.-The combination in a carrier. wave detector, of an electron discharge device having a cathode and a plurality of anodes, a circuit connected between said anodes tunedto the frequency of the carrier wave to be detected, means for producing a magnetic field between said anodes and cathode, means for impressing a received earner wave upon said tuned circuit, and means connected to respond tosthe space current in said discharge device.

In witness whereof, I have hereuntoset my hand this 18th day of April, 1929.

ELMER 'D. MoARTHUR. 

